WEDNESDAY, June 16 (HealthDay News) -- Researchers report they've moved a step closer to treating HIV patients with gene therapy that could potentially one day keep the AIDS-causing virus at bay.

The study, published in the June 16 issue of the journal Science Translational Medicine, only looked at one step of the gene therapy process, and there's no guarantee that genetically manipulating a patient's own cells will succeed or work better than existing drug therapies.

Still, "we demonstrated that we could make this happen," said study lead author David L. DiGiusto, a biologist and immunologist at City of Hope, a hospital and research center in Duarte, Calif. And the research took place in people, not in test tubes.

Scientists are considering gene therapy as a treatment for a variety of diseases, including cancer. One approach involves inserting engineered genes into the body to change its response to illness.

In the new study, researchers genetically manipulated blood cells to resist HIV and inserted them into four HIV-positive patients who had lymphoma, a blood cancer.

The patients' healthy blood cells had been stored earlier and were being transplanted to treat the lymphoma.

Ideally, the cells would multiply and fight off HIV infection. In that case, "the virus has nowhere to grow, no way to expand in the patient," DiGiusto said.

At this early point in the research process, however, the goal was to see if the implanted cells would survive. They did, remaining in the bloodstreams of the subjects for two years.

In the next phases of research, scientists will try to implant enough genetically engineered cells to actually boost the body's ability to fight off HIV, DiGiusto said.

Plenty of caveats still exist. The research, as DiGiusto said, is experimental. And there's the matter of cost: He estimated that the price for gene therapy treatment for HIV patients could run about as much as a bone marrow transplant. Those cost about $100,000.

On the other hand, gene therapy has the potential to free HIV patients from a lifetime of taking medications that may fail to work, especially if the virus develops immunity to them, said David V. Schaffer, co-director of the Berkeley Stem Cell Center at the University of California at Berkeley and co-author of a commentary accompanying DiGiusto's study.

Over time, the savings on medications could outweigh the cost of the gene therapy, he noted.

The treatment wouldn't necessarily be a cure because the virus would remain in the body. Still, it could create a situation "where HIV is present but at levels that are too low to detect and don't cause AIDS," Schaffer said.

More information

For more about gene therapy, visit the U.S. National Library of Medicine.